Implement style invalidation tree walk for targeted style recalc upon class change.

Source/core/dom/Element.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2001 Peter Kelly (pmk@post.com)
  *           (C) 2001 Dirk Mueller (mueller@kde.org)
  *           (C) 2007 David Smith (catfish.man@gmail.com)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2012, 2013 Apple Inc. All rights reserved.
  *           (C) 2007 Eric Seidel (eric@webkit.org)
  *
  * This library is free software; you can redistribute it and/or
@@ skipping 1027 matching lines @@
     unsigned length = newClassString.length();
 
     if (!length)
         return false;
 
     if (newClassString.is8Bit())
         return classStringHasClassName(newClassString.characters8(), length);
     return classStringHasClassName(newClassString.characters16(), length);
 }
 
-template<typename Checker>
-static bool checkSelectorForClassChange(const SpaceSplitString& changedClasses, const Checker& checker)
-{
-    unsigned changedSize = changedClasses.size();
-    for (unsigned i = 0; i < changedSize; ++i) {
-        if (checker.hasSelectorForClass(changedClasses[i]))
-            return true;
-    }
-    return false;
-}
-
-template<typename Checker>
-static bool checkSelectorForClassChange(const SpaceSplitString& oldClasses, const SpaceSplitString& newClasses, const Checker& checker)
-{
-    if (!oldClasses.size())
-        return checkSelectorForClassChange(newClasses, checker);
-
-    // Class vectors tend to be very short. This is faster than using a hash table.
-    BitVector remainingClassBits;
-    remainingClassBits.ensureSize(oldClasses.size());
-
-    for (unsigned i = 0; i < newClasses.size(); ++i) {
-        bool found = false;
-        for (unsigned j = 0; j < oldClasses.size(); ++j) {
-            if (newClasses[i] == oldClasses[j]) {
-                // Mark each class that is still in the newClasses so we can skip doing
-                // an n^2 search below when looking for removals. We can't break from
-                // this loop early since a class can appear more than once.
-                remainingClassBits.quickSet(j);
-                found = true;
-            }
-        }
-        // Class was added.
-        if (!found && checker.hasSelectorForClass(newClasses[i]))
-            return true;
-    }
-
-    for (unsigned i = 0; i < oldClasses.size(); ++i) {
-        if (remainingClassBits.quickGet(i))
-            continue;
-        // Class was removed.
-        if (checker.hasSelectorForClass(oldClasses[i]))
-            return true;
-    }
-
-    return false;
-}
-
 void Element::classAttributeChanged(const AtomicString& newClassString)
 {
     StyleResolver* styleResolver = document().styleResolver();
     bool testShouldInvalidateStyle = inActiveDocument() && styleResolver && styleChangeType() < SubtreeStyleChange;

[ojan, 2014/01/30 19:08:39]

Hmmm...as an aside, I think this code might be wrong. If you change a classname
when there's no styleResolver, we won't mark the element as needing a recalc.
All the more reason to get rid of the throwaway timer.

[chrishtr, 2014/01/30 19:25:48]

yikes.

-    bool shouldInvalidateStyle = false;
 
     if (classStringHasClassName(newClassString)) {
         const bool shouldFoldCase = document().inQuirksMode();
         const SpaceSplitString oldClasses = elementData()->classNames();
         elementData()->setClass(newClassString, shouldFoldCase);
         const SpaceSplitString& newClasses = elementData()->classNames();
-        shouldInvalidateStyle = testShouldInvalidateStyle && checkSelectorForClassChange(oldClasses, newClasses, styleResolver->ensureRuleFeatureSet());
+        if (testShouldInvalidateStyle)
+            styleResolver->ensureRuleFeatureSet().scheduleStyleInvalidationForClassChange(oldClasses, newClasses, this);
     } else {
         const SpaceSplitString& oldClasses = elementData()->classNames();
-        shouldInvalidateStyle = testShouldInvalidateStyle && checkSelectorForClassChange(oldClasses, styleResolver->ensureRuleFeatureSet());
+        if (testShouldInvalidateStyle)
+            styleResolver->ensureRuleFeatureSet().scheduleStyleInvalidationForClassChange(oldClasses, this);
         elementData()->clearClass();
     }
 
     if (hasRareData())
         elementRareData()->clearClassListValueForQuirksMode();
-
-    if (shouldInvalidateStyle)
-        setNeedsStyleRecalc();
 }
 
 bool Element::shouldInvalidateDistributionWhenAttributeChanged(ElementShadow* elementShadow, const QualifiedName& name, const AtomicString& newValue)
 {
     ASSERT(elementShadow);
     const SelectRuleFeatureSet& featureSet = elementShadow->ensureSelectFeatureSet();
 
     if (isIdAttributeName(name)) {
         AtomicString oldId = elementData()->idForStyleResolution();
         AtomicString newId = makeIdForStyleResolution(newValue, document().inQuirksMode());
         if (newId != oldId) {
             if (!oldId.isEmpty() && featureSet.hasSelectorForId(oldId))
                 return true;
             if (!newId.isEmpty() && featureSet.hasSelectorForId(newId))
                 return true;
         }
     }
 
     if (name == HTMLNames::classAttr) {
         const AtomicString& newClassString = newValue;
         if (classStringHasClassName(newClassString)) {
             const bool shouldFoldCase = document().inQuirksMode();
             const SpaceSplitString& oldClasses = elementData()->classNames();
             const SpaceSplitString newClasses(newClassString, shouldFoldCase);
-            if (checkSelectorForClassChange(oldClasses, newClasses, featureSet))
+            if (featureSet.checkSelectorsForClassChange(oldClasses, newClasses))
                 return true;
         } else {
             const SpaceSplitString& oldClasses = elementData()->classNames();
-            if (checkSelectorForClassChange(oldClasses, featureSet))
+            if (featureSet.checkSelectorsForClassChange(oldClasses))
                 return true;
         }
     }
 
     return featureSet.hasSelectorForAttribute(name.localName());
 }
 
 // Returns true is the given attribute is an event handler.
 // We consider an event handler any attribute that begins with "on".
 // It is a simple solution that has the advantage of not requiring any
@@ skipping 2468 matching lines @@
     // Before doing so, we need to resolve issues in HTMLSelectElement::recalcListItems
     // and RenderMenuList::setText. See also https://bugs.webkit.org/show_bug.cgi?id=88405
     if (hasTagName(optionTag) || hasTagName(optgroupTag))
         return false;
     if (FullscreenElementStack::isActiveFullScreenElement(this))
         return false;
     return true;
 }
 
 } // namespace WebCore